1. Field of the Invention
The present invention relates to unlicensed mobile access networks, and more particularly to the support of location services in such networks.
2. Description of the Related Art
“Unlicensed Mobile Access” (UMA) is a proposal to create a BSS (base station sub-system) look-alike access system architecture for “tunneled GSM” over two existing unlicensed-band radio interfaces: Bluetooth and WiFi (802.11). It is proposed that UMA may be used, for example, for coverage extensions in indoor applications (such as home or office applications) to capture otherwise fixed line traffic for cellular operators. In the US, UMA is perceived as a cheaper way to provide missing coverage to domestic users at home than via a macro network.
There is a current European proposal to use UMA architectures in combination with a GSM (global system for mobile communication) RAN (radio access network), known as a GERAN. The unlicensed mobile access network (UMAN) is proposed to consist of UMA network controllers (UNCs), and access points (APs), which APs conform to a BlueTooth or WiFi standard as appropriate.
The UMA signaling protocol architecture for circuit switched domain (between a mobile station, an access point, and an UNC) is shown in FIG. 1.
A consortium of companies (reference can be made to http://www.umatechnology.org/) have drafted specifications for UMANs. Location Services in UMA
At least some of these UMAN specifications include some discussion of location services (LCS).
The published document “UMA Architecture (Stage 2) R1.0.2” discusses LCS support. Specifically discussed is emergency service support for United States Federal Communications Code (FCC) E911 Phase 2 requirements. A number of ways in which the location of a terminal performing an emergency call may be obtained are discussed (in chapter 9.17.2.1). In one way the UNC may maintain a database of AP locations. The AP location is provided from a terminal via a known URR REGISTER REQUEST/URR REGISTER UPDATE message or via some management interface. In another way the terminal may provide its current location (e.g. obtained via the A-GPS interface) in a URR REGISTER/UPDATE message. In another way the UNC can look up a location database based on a public IP address and/or MAC address of a terminal.
Location services are discussed in chapter 9.18 of the published document “UMA Architecture (Stage 2) R1.0.2”. Cell information (of possibly available GSM coverage) may be used by the UNC to determine the location of a terminal. As another possibility, the AP identity is mentioned. Cell and AP information can be provided from the terminal to the UNC using URR-REGISTER and URR-REGISTER UPDATE messages.
Likewise, the document “UMA Protocols (Stage 3) R1.0.2” discusses LCS support. URR REGISTER REQUEST and URR REGISTER UPDATE UPLINK messages are identified as including the following information elements (IE) useful for location purposes: AP radio identity; cell identity; Geographic Location; and AP location. AP radio identity IE is used for transmission of Bluetooth Device address (BD_ADDR) or WLAN MAC Address of AP. There is a field called “Type of Identity” which contains only a value “IEEE MAC-address format”. Other values are for future use. A cell identity IE identifies the cellular cell. A geographic location IE can be used to deliver, for example, an A-GPS location estimate from the terminal. An AP location IE is for indicating the location of a terminal or an AP to the network.
T-Mobile USA has proposed in the UMA Forum that the Lb interface should be used between a UMA network controller (UNC) and a serving mobile location centre (SMLC). The Lb interface is the 3GPP GERAN standardized interface between a base station controller (BSC) and the SMLC. The Lb interface and the protocol stack between a SMLC, BSC, and Mobile Station (MS) (as described in 3GPP TS 43.059 v6.4.0) is shown in FIG. 3.
The RRLP (Radio Resource LCS Protocol) is a protocol that defines the location related information exchanged directly between a MS and the SMLC. Currently the RRLP supports Enhanced Observed Time Difference (E-OTD), Global Positioning System (GPS), and Assisted GPS (A-GPS) location methods.
The proposal from T-Mobile USA to use the 3GPP standardized Lb interface between an UNC and a SMLC provides for the possibility to reuse existing GERAN SMLCs in the UMAN. However a problem with UMA specifications, as can be seen from the document “UMA Protocols (Stage3) R1.0.2, is that there is no mechanism to deliver E-OTD, GPS, or A-GPS related information from the UNC towards mobile stations. There are no messages or information elements available that could include such information.
While E-OTD, which requires that the mobile station can receive signals from at least three separate base station sites, may not usually be a feasible location method with UMA, A-GPS can be expected to be an important solution for UMA.